Shanghai Futures Exchange copper fell 1.8 percent to 37,040 yuan ($5,715) a tonne on Wednesday, off the day's low of 36,920 yuan ($5,697) - the weakest since March 9. Copper slips on simmering concerns over global economic growth, although a softer dollar after the US Federal Reserve chair stressed the need for caution on interest rate hikes checked losses.
China's bonded copper stocks have risen 100,000 in March to 500,000, while Shanghai stocks doubled year-to-date to just under 400,000 earlier in March before falling last week.
In other metals, Shanghai tin nickel and lead closed down by more than 2 percent.
"The markets in effect did a little too much too soon. While there has certainly been some improvements in order books, reduction in some stock levels and production cutbacks, turning markets around is like turning a super tanker and that takes time," said broker Kingdom Futures in a note.